US7587936B2ActiveUtilityPatentIndex 93
Apparatus and method for determining drilling fluid acoustic properties
Est. expiryFeb 1, 2027(~0.6 yrs left)· nominal 20-yr term from priority
Inventors:HAN WEI
E21B 47/085E21B 47/01
93
PatentIndex Score
46
Cited by
161
References
21
Claims
Abstract
Aspects of this invention include a downhole tool having first and second radially offset ultrasonic standoff sensors and a controller including instructions to determine at least one of a drilling fluid acoustic velocity and a drilling fluid attenuation coefficient from the reflected waveforms received at the standoff sensors. The drilling fluid acoustic velocity may be determined via processing the time delay between arrivals of a predetermined wellbore reflection component at the first and second sensors. The drilling fluid attenuation coefficient may be determined via processing amplitudes of the predetermined wellbore reflection coefficients. The invention advantageously enables the acoustic velocity and attenuation coefficient of drilling fluid in the borehole annulus to be determined in substantially real-time.
Claims
exact text as granted — not AI-modifiedI claim:
1. A downhole measurement tool, comprising:
a substantially cylindrical tool body having a cylindrical axis;
first and second standoff sensors deployed on the tool body, the standoff sensors being radially offset from one another with respect to the longitudinal axis, each of the standoff sensors configured to (i) transmit an ultrasonic pressure pulse into a borehole and (ii) receive a reflected waveform; and
a controller including instructions for determining a drilling fluid acoustic velocity according to the following equation:
c
f
=
2
L
2
-
2
L
1
T
2
-
T
1
≈
2
L
0
Δ
T
wherein c f represents the drilling fluid acoustic velocity, L 1 and L 2 represent standoff distances at the first and second standoff sensors, L 0 represents a radial offset distance between the first and second standoff sensors, T 1 and T 2 represent arrival times of wellbore reflection components received at the first and second standoff sensors, and ΔT represents a difference between the arrival times.
2. The downhole measurement tool of claim 1 , wherein the first and second standoff sensors are radially offset the distance in the range from about 0.25 to about 0.5 inches.
3. The downhole measurement tool of claim 1 , wherein the first and second standoff sensors are longitudinally offset a distance of less than about 1 foot.
4. The downhole measurement tool of claim 1 , wherein the first and second standoff sensors are deployed at substantially the same circumferential position on the tool body.
5. The downhole measurement tool of claim 1 , wherein:
the tool body is configured for coupling with a drill string; and
the measurement tool further comprises at least one logging while drilling sensor.
6. The downhole measurement tool of claim 5 , wherein the logging while drilling sensor comprises at least one nuclear density sensor.
7. A method for determining an acoustic velocity of drilling fluid in a borehole, the method comprising:
(a) deploying a tool in the borehole, the tool including first and second transducers, the transducers being radially offset from one another with respect to a longitudinal axis of the tool;
(b) causing the first and second transducers to transmit corresponding first and second acoustic signals;
(c) causing the first and second transducers to receive corresponding first and second reflected signals from the acoustic signals transmitted in (b);
(d) determining a time delay between a predetermined wellbore reflection component of the corresponding first and second reflected signals received in (c); and
(e) processing the time delay determined in (d) to determine the acoustic velocity of the drilling fluid according to the equation:
c
f
=
2
L
2
-
2
L
1
T
2
-
T
1
≈
2
L
0
Δ
T
wherein c f represents the acoustic velocity of the drilling fluid, L 1 and L 2 represent standoff distances at the first and second transducers, L 0 represents a radial offset distance between the first and second transducers, T 1 and T 2 represent arrival times of the predetermined wellbore reflection components received at the first and second standoff sensors, and ΔT represents the time delay.
8. The method of claim 7 , further comprising:
(f) determining first and second amplitudes of a wellbore reflection component of the corresponding first and second reflected signals received in (c); and
(g) processing the first and second amplitudes determined in (f) to determine an attenuation coefficient of the drilling fluid.
9. The method of claim 7 , wherein the transducers are further (i) axially offset from one another and (ii) circumferentially aligned with one another.
10. The method of claim 7 , wherein the first and second transducers are deployed on a logging while drilling tool.
11. The method of claim 7 , further comprising:
(f) comparing a plurality of the time delays determined in (d); and
(g) determining the acoustic velocity in (e) only when a deviation of the time delays compared in (f) is less than a predetermined threshold.
12. A method for determining an attenuation coefficient of drilling fluid in a borehole, the method comprising:
(a) deploying a tool in the borehole, the tool including first and second transducers, the transducers being radially offset from one another with respect to a longitudinal axis of the tool;
(b) causing the first and second transducers to transmit corresponding first and second acoustic signals;
(c) causing the first and second transducers to receive corresponding first and second reflected signals the acoustic signals transmitted in (b);
(d) determining an amplitude of a first predetermined component of each of the corresponding first and second reflected signals received in (c); and
(e) processing the amplitudes determined in (d) to determine the attenuation coefficient of the drilling fluid according to at least one equation selected from the group consisting of:
α
=
1
2
(
L
2
-
L
1
)
(
ln
(
V
1
b
V
2
b
)
-
ln
(
K
1
K
2
)
)
=
1
2
(
L
2
-
L
1
)
ln
(
V
1
b
K
2
V
2
b
K
1
)
;
α
=
1
2
(
L
2
-
L
1
)
(
ln
(
V
1
b
V
2
b
)
-
ln
(
V
1
i
V
2
i
)
)
=
1
2
(
L
2
-
L
1
)
ln
(
V
1
b
V
2
i
V
2
b
V
1
i
)
;
and
α
=
1
2
L
0
(
ln
(
V
1
b
V
2
b
)
-
ln
(
V
1
i
V
2
i
)
)
=
1
2
L
0
ln
(
V
1
b
V
2
i
V
2
b
V
1
i
)
wherein α represents the attenuation coefficient of the drilling fluid, L 1 and L 2 represent standoff distances at the first and second transducers, L 0 represents a radial offset distance between the first and second transducers, K 1 and K 2 represent characteristic parameters of the corresponding first and second transducers. V 1i and V 2i represent amplitudes of interface reflection components received at the corresponding first and second transducers, and V 1b and V 2b represent amplitudes of wellbore reflection components received at the corresponding first and second standoff sensors.
13. The method of claim 12 , wherein the transducers are further (i) axially offset from one another and (ii) circumferentially aligned with one another.
14. The method of claim 12 , further comprising:
(f) determining a time delay between a predetermined wellbore reflection component of the corresponding first and second reflected signals received in (c); and
(g) processing the time delay determined in (f) to determine an acoustic velocity of the drilling fluid.
15. The method of claim 12 , wherein the first and second transducers are deployed on a logging while drilling tool.
16. A downhole measurement tool, comprising:
a substantially cylindrical tool body having a cylindrical axis;
first and second standoff sensors deployed on the tool body, the standoff sensors being radially offset from one another with respect to the longitudinal axis, each of the standoff sensors configured to (i) transmit an ultrasonic pressure pulse into a borehole and (ii) receive a reflected waveform; and
a controller including instructions for determining a drilling fluid attenuation coefficient according to at least one equation selected from the group consisting of:
α
=
1
2
(
L
2
-
L
1
)
(
ln
(
V
1
b
V
2
b
)
-
ln
(
K
1
K
2
)
)
=
1
2
(
L
2
-
L
1
)
ln
(
V
1
b
K
2
V
2
b
K
1
)
;
α
=
1
2
(
L
2
-
L
1
)
(
ln
(
V
1
b
V
2
b
)
-
ln
(
V
1
i
V
2
i
)
)
=
1
2
(
L
2
-
L
1
)
ln
(
V
1
b
V
2
i
V
2
b
V
1
i
)
;
and
α
=
1
2
L
0
(
ln
(
V
1
b
V
2
b
)
-
ln
(
V
1
i
V
2
i
)
)
=
1
2
L
0
ln
(
V
1
b
V
2
i
V
2
b
V
1
i
)
wherein α represents the drilling fluid attenuation coefficient, L 1 and L 2 represent standoff distances at the first and second standoff sensors, L 0 represents a radial offset distance between the first and second standoff sensors, K 1 and K 2 represent characteristic parameters of the corresponding first and second standoff sensors, V 1i and V 2i represent amplitudes of interface reflection components received at the corresponding first and second standoff sensors, and V 1b and V 2b represent amplitudes of wellbore reflection components received at the corresponding first and second standoff sensors.
17. The downhole measurement tool of claim 16 , wherein the first and second standoff sensors are radially offset the distance in the range from about 0.25 to about 0.5 inches.
18. The downhole measurement tool of claim 16 , wherein the first and second standoff sensors are longitudinally offset a distance of less than about 1 foot.
19. The downhole measurement tool of claim 16 , wherein the first and second standoff sensors are deployed at substantially the same circumferential position on the tool body.
20. The downhole measurement tool of claim 16 , wherein:
the tool body is configured for coupling with a drill string; and
the measurement tool further comprises at least one logging while drilling sensor.
21. The downhole measurement tool of claim 20 , wherein the logging while drilling sensor comprises at least one nuclear density sensor.Cited by (0)
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